#include <iostream>
using namespace std;
int main(){
	int sum = 0;
	int number;
	
	cout << "Please input the number you want to cal sum:" << endl;
	cin >> number;
	
	for(int i = 0;i <= number;i++){
		sum += i;
	}
	cout << "The resulf of sum:" << sum << endl;
	
	return 0;
}
